You could get a tax credit of up to $8000 on this year's tax return or next year's return. The stimulus package offers a tax credit equal to 10% of the purchase price of your first home up to an $80,000 home purchase price. This applies to homes purchased between January 1, 2009 and Dec 1, 2009.
Unlike last year's tax credit you don't even have to pay it back, unless you sell the home within 3 years.
Energy Star water heaters, AC and Heat units
Energy efficient doors and windows